Solenoid valves as a type of valves known per se are used in vehicles, for instance, commercial vehicles, which may be for converting electrical control pulses to, inter alia, hydraulic or pneumatic control pulses for controlling automatically or electronically controlled gear units, for example, or electronic brake systems.
In practical applications of that kind, as a rule, the valves are operated with the aid of a circuit configuration in a control unit with a pulse width modulation, the circuit configuration having a switchover possibility for a rapid and slow quenching, i.e., a rapid or slow de-energizing of the magnetic field in the coils of the valves. Until now, if several valves were present, several such circuit configurations would have to be used corresponding to the number of valves.
FIG. 2 shows, in simplified form, a known circuit configuration for the pulse width modulation and quenching of a single solenoid valve.
The known circuit configuration according to FIG. 2 essentially includes a first switch S0, a second switch S1, an inductor L1 representing the coil of the solenoid valve and a diode D1, a supply line V for the voltage supply of the circuit device, a feedback line R for feeding back a state of the circuit configuration to a control device (not shown), and a line PWM for the input of a pulse width modulation into the circuit configuration via first switch S0.
Going into detail, second switch S1 and diode D1 are interconnected in series in a first branch of the circuit configuration, and this series interconnection is interconnected in parallel with inductor L1, disposed in a second branch of the circuit configuration, between supply line V and feedback line R. The parallel interconnection with inductor L1 on one hand and second switch S1 and diode D1 on the other hand is then connectable to a ground potential M via first switch S0 to which the pulse width modulation is applied.
The disadvantages in the known circuit configuration, which is requisite in this form for each inductor L1 to be controlled in a solenoid valve, are, in particular, that two switches S0, S1 are necessary for each inductor L1, that only one shutdown path is available per inductor L1, and that at the instant the magnetic field of the inductor is shut down, a synchronization of the two switches S0, S1 is necessary.
This disadvantageously results, therefore, in increased expenditure for components as well as a more complex control, which particularly in the vehicle sector, is reflected in undesirably high costs and high development expenditure. In addition, a higher number of components in the overall system involves a higher risk of breakdown, and can thereby lead to decreased economic efficiency of the vehicle.
Moreover, the prior publication DE 101 50 752 A1 describes a valve driver, in which a valve coil, a disconnect device and a switching device are arranged serially and a freewheeling device is arranged in parallel with respect to the valve coil and the disconnect device. In this configuration, the pulse width modulation is switched off through the switching device in response to a high-speed de-excitation of the valve coil by way of the disconnect device, so that in each case, only one valve coil is able to be de-excited at high speed, and therefore a separate valve driver continues to be necessary for each valve coil.